Leganes grew into the game after the break as Real's thoughts perhaps turned towards Bayern, and Miguel Guerrero wasted an excellent chance to halve the deficit as he headed wide from a Nabil El Zhar cross.
It might not have been the most dramatic bicycle-kick in the business but Bale nevertheless managed to acrobatically turn the ball into the net with just four minutes on the clock after Karim Benzema's initial effort had fallen helpfully into his path.
Up ahead in midfield, Zidane could rest his trusted trident of Casemiro, Luka Modric and Toni Kroos, which should see the likes of Dani Ceballos, Mateo Kovacic and Marcos Llorente returning to the starting lineup. Leganes cut the deficit in half in the 66th minute.
Bale was one of the new faces and he hooked home from six yards before Borja Mayoral converted a second from a yard.
Real Madrid beat Leganes 2-1 in La Liga Saturday after coach Zinedine Zidane heavily rotated his side in preparation for Tuesday's Champions League semi-final second leg against Bayern Munich, including leaving out top-scorer Cristiano Ronaldo. Amrabat was played into space on the right and he advanced to the byline before squaring to an open Brasanac, who had the simplest of tap-ins from close range. Meanwhile, Zidane commented on Nacho's injury situation in his pre-match press conference, iterating that the Spaniard is making good progress on his return.
And much like his manager, the frontman called on the club's supporters to help drive Real Madrid to their third successive European Cup final. "The attitude was exemplary".
"We are going to take part in a huge match".
"I don't know how significant the first-leg advantage will be in the Champions League". We'll have to play like we never have before this year: we need concentration, determination, commitment, to win battles.